The present invention relates generally to photoionization, and more particularly to using a single pulsed ultraviolet laser to ionize an air-fuel mixture to improve ignition of gas turbine and other engines.
Gas turbine and other engines require igniting an air-fuel mixture, generally in a combustion chamber section of the engine. Most prior art gas turbine igniters work by generating high tension electrical sparks, or arcs, across a pair of electrodes. The sparks are triggered by a very high voltage electric field across the electrodes generated by conventional induction coils or by other methods.
As described in U.S. Pat. No. 5,673,550 to Few et al, “spark igniters are typically positioned at a peripheral, non-optimal position of a combustion chamber, while the fuel spray to be ignited is located in a central portion adjacent to a fuel injector.” As also described in the Few et al. patent, spark igniters will degrade over time and can cause engine failure.
The Few et al. patent, as well as U.S. Pat. No. 6,394,788 to Early et al. and other prior art, describe how a laser igniter, using laser light to ignite an air-fuel mixture and begin combustion, could solve many of the problems of spark igniters.
Unfortunately, as described in that prior art, present art laser igniters typically require very high power pulsed lasers to create a high-field breakdown of air and photoelectric effects at an electrode surface. The practical issues of gaining optical access to an ignition volume and integrating a high power pulsed laser near the engine and near the combustion area have been a specific concern.
The primary unrealized goal of the prior art has been to be able to create an ionized channel using a low energy source.
A related unrealized goal of the prior art has been a laser igniter that can guide a lower power laser pulse through a fiber optic cable into an ignition region and still reliably induce ignition of an air-fuel mixture.